1. Field of The Invention
The present invention relates generally to fluid delivery devices. More particularly, the invention concerns an improved fluid delivery apparatus for precise subdermal delivery over time of medicinal liquids to an ambulatory patient, the device including a unique collapsible needle cover and a novel septum anti-invasion feature.
2. Discussion of The Prior Art
A number of different types of liquid dispensers for dispensing medicaments to ambulatory patients have been suggested. Many of the devices seek either to improve or to replace the traditional hypodermic syringe which has been the standard for delivery of liquid medicaments such as insulin solution or other beneficial agents such as hormones, peptides, and biologically active agents.
Those patients that require frequent injections of the same or different amounts of medicament, find the use of the hypodermic syringe both inconvenient and unpleasant. Further, for each injection, it is necessary to first draw the injection dose into the syringe, then check the dose and, after making certain that all air has been expelled from the syringe, finally, inject the dose. This cumbersome and tedious procedure creates an unacceptable probability of debilitating complications, particularly for the elderly and the infirm. Further, the act of inserting a needle into the skin is a practice some new patients, especially pediatric patients, may find traumatic thus adding to the discomfort they may experience during therapy.
One example of the urgent need for an improved liquid delivery device for ambulatory patients can be found in the stringent therapeutic regimens used by insulin-dependent diabetics. The therapeutic objective for diabetics is to consistently maintain blood glucose levels within a normal range much as the normally functioning pancreas would do by secreting a very low level of extremely fast-acting insulin at a basal rate into the blood stream throughout the day and night.
Consider the normal individual who doesn't have diabetes, this individual's cells require energy throughout the day just to maintain a basal metabolic rate. This energy is supplied to the cells by glucose that is transported from the bloodstream to the cells by insulin. When food is consumed, the blood glucose level rises and the pancreas responds by releasing a surge of fast-acting insulin. To mimic this natural process with individual injections, the patient would have to continuously administer minuscule amounts of fast-acting insulin every few minutes throughout the day and night.
Conventional therapy usually involves injecting, separately, or in combination, fast-acting and slower-acting insulin by syringe several times a day. The dose must be calculated based on glucose levels present in the blood. Slower-acting insulin is usually administered in the morning and evening to take advantage of longer periods of lower level glucose uptake. Fast-acting insulin is usually injected prior to meals. If the dosage of fast-acting insulin is off, the bolus administered may lead to acute levels of either glucose or insulin resulting in complications, including unconsciousness or coma. Over time, high concentrations of glucose in the blood together with the absence of hormone insulin can also lead to a variety of chronic health problems, such as vision loss, kidney failure, heart disease, nerve damage, and amputations.
A recently completed study entitled The Diabetes Control and Complications Trial (DCCT) sponsored by the National Institutes of Health (NIH) investigated the effects of different therapeutic regimens on the health outcomes of insulin-dependent diabetics. This study revealed some distinct advantages in the adoption of certain therapeutic regimens. Intensive therapy that involved intensive blood glucose monitoring and more frequent, multiple injections of insulin by conventional means, for example, syringes, throughout the day saw dramatic decreases in the incidence of debilitating complications.
The NIH study also raises the question of practicality and patient adherence to an intensive therapy regimen. A bona fide improvement in insulin therapy management must focus on the facilitation of patient comfort and convenience as well as dosage and administration schemes. Basal rate delivery of insulin or other diabetes related therapeutic agents by means of a convenient and reliable delivery device over an extended period of time represents one means of improving diabetes management. Basal rate delivery involves the delivery of very small volumes of fluid (for example, 0.3-3 mL. depending on body mass) over comparatively long periods of time (18-24) hours). As will be appreciated from the discussion which follows, the apparatus of the present invention is uniquely suited to provide precise fluid delivery management at a low cost in those cases where a variety of precise dosage schemes are of utmost importance.
An additional important feature of the apparatus of the present invention is the provision of a novel reservoir filling means disposed on the underside of the base.
Another feature of the improved apparatus of the invention comprises a novel reservoir fill adapter means for permitting the reservoir of the device to be filled by syringe-type filling means, the fill adapter being removable from the delivery device following reservoir filling.
Another feature of the improved apparatus of the invention comprises a novel septum anti-invasion means which prevents refilling of the reservoir of the device following use.
Still another important aspect of the invention is the provision of novel, collapsible needle covers of various designs which, during the injection step, crush, collapse or retract to permit insertion of the needle into the patient. These novel needle covers enable a patient to use the device without being aware of the insertion of a needle into the skin while at the same time maintaining the aseptic presentation of the cannula.
With regard to the prior art, one of the most versatile and unique fluid delivery apparatus developed in recent years is that developed by one of the present inventors and described in U.S. Pat. No. 5,205,820. The components of this novel fluid delivery apparatus generally include: a base assembly, an elastomeric membrane serving as a stored energy means, fluid flow channels for filling and delivery, flow control means, a cover, and an ullage which comprises a part of the base assembly.
Another useful liquid delivery device is that described in U.S. Pat. No. 5,514,097 issued to Knauer. The Knauer device comprises a medicament injection apparatus for subcutaneous or intramuscular delivery of a medicament which conceals the infusion needle behind a needle shroud. On apparatus activation, the needle is thrust forward, pushing the needle tip outside the needle shroud with enough force to puncture the skin. The needle is thus automatically introduced into the tissue at the proper needle/skin orientation. In the same action, the apparatus automatically dispenses an accurate pre-set dose.
U.S. Pat. No. 5,226,896 issued to Harris also describes a useful prior art device. This device comprises a multidose syringe having the same general appearance as a pen or mechanical pencil. The Harris device is specifically adapted to provide for multiple measured injections of materials such as insulin or human growth hormones.
Still another type of liquid delivery device is disclosed in U.S. Pat. No. 4,592,745 issued to Rex et al. This device is, in principle, constructed as a hypodermic syringe, but differs in that it enables dispensing of a predetermined portion from the available medicine and in that it dispenses very accurate doses.
The present invention seeks to significantly improve over the prior art by providing a novel fluid delivery device having unique filling and delivery means for filling the fluid reservoir of the device and for safely and precisely dispensing medicinal fluids therefrom.